A protein group called complement includes proteins indicated as C1 to C9, and these proteins are successively activated through three different pathways (classical pathway, lectin pathway, alternative pathway) to elicit immune response. The fifth complement component, C5, is cleaved to C5a and C5b by C5 convertase. C5a is called anaphylatoxin, and induces inflammatory response for various cells via CSaR (CD88) and C5L2 (GPR77). C5b sequentially reacts with C6 to C9 to be converted into a membrane attack complex (MAC) as a final product, which causes bacteriolysis to pathogens or cell lysis. The complement system may elicit strong cytotoxicity to host cells if the complement system fails to be suitably controlled or is excessively activated.
From previous studies, the complement C5 is known to be associated with various diseases including paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), myasthenia gravis (MG), neuromyelitis optica (NMO), antibody-mediated rejection in kidney transplantation, Guillain-Barre syndrome, antineutrophil cytoplasmic antibody-associated vasculitis (ANCA-associated vasculitis), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), autoimmune encephalitis, IgG4-related diseases, asthma, antiphospholipid antibody syndrome, ischemia-reperfusion injury, typical hemolytic uremic syndrome (tHUS), multifocal motor neuropathy (MMN), multiple sclerosis (MS), thrombotic thrombocytopenic purpura (TTP), spontaneous abortion, habitual abortion, traumatic brain injury, cold agglutinin disease, dermatomyositis, hemolytic uremic syndrome associated with Shigatoxin-producing Escherichia coli (E. coli), graft dysfunction, myocardial infarction, sepsis, atherosclerosis, septic shock, spinal cord injury, psoriasis, autoimmune hemolytic anemia (AIHA), antiphospholipid syndrome (APS), myocarditis, immune complex vasculitis, Takayasu's disease, and Kawasaki's disease (arteritis). Thus, inhibition or suppression of expression of complement C5 is expected to lead to successful treatment of these diseases. In particular, inhibition of complement C5 is suggested to be effective for treating or preventing paroxysmal nocturnal hemoglobinuria (Non Patent Literature 1), atypical hemolytic uremic syndrome (Non Patent Literature 2), myasthenia gravis (Non Patent Literature 3), neuromyelitis optica (Non Patent Literature 4), and antibody-mediated kidney transplant rejections (Non Patent Literature 5).
The anti-C5 monoclonal antibody eculizumab (Soliris (registered trademark)) exhibits high affinity for complement C5, and suppresses excessive activation of the complement through inhibition of cleavage of C5 into C5a/C5b and accompanying formation of a membrane attack complex. Thereby, eculizumab exhibits inhibitory effect on hemolysis, and thus is known as a therapeutic agent for paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. In addition, eculizumab is known as a therapeutic agent for generalized myasthenia gravis (gMG). However, eculizumab is very expensive, and hence development of alternative means applicable to treatment and prevention of complement C5-mediated diseases is desired.
Examples of methods for suppressing expression of complement C5 include methods utilizing RNA interference (hereinafter, also referred to as “RNAi”). For example, a double-stranded ribonucleic acid (dsRNA) agent is known, which induces cleavage of an RNA transcript of the C5 gene via an RNA-induced silencing complex (RISC) (Patent Literature 1).